This invention relates to joining together heated workpieces for processing in a rolling mill or the like, and more particularly, to joining together heated workpieces to form a continuous stream of a predetermined number of individual workpieces by introducing a quantity of liquid-weld metal into a predetermined gap established between the ends of two workpieces and allowing the weld metal to solidify while the workpieces are advanced continuously and while the forward end of the leading workpiece is processed in a rolling mill.
In the past, it was a practice to roll a workpiece, e.g., a bloom in a billet mill and then without reheating the workpiece, roll the workpiece, e.g., a billet in a bar mill. However, in some rolling operations a reheat furnace was used to heat the billet after rolling in the billet mill before the rolling operations continued in the bar mill. The use of a reheat furnace greatly reduces the wide temperature range and, therefore, reduces the harmful affects to the billet material before completion of the rolling operation. More recently, workpieces for processing in a bar mill are produced with a desired cross section by a continuous-casting facility. A reheat furnace is used to heat desired lengths of the continuous-cast workpieces for rolling in a bar mill. The selection of the workpieces which are fed to a bar mill is based on a desired length of the rolled product which can be coiled or straight products that are subdivided into convenient lengths. However, it is necessary to compensate for a loss of yield, i.e., the loss of salable product due to the cropped end losses and cobbles. A cobble occurs when the workpiece fails to pass along an intended course of travel between rolling mill stands in a given rolling mill installation. These losses are heretofore common because crop shears are used to cut a length of material from the leading end and sometimes the trailing end of the workpiece. With a continuous strand of billets, these leading edges are minimized, thereby reducing a loss of yield due to cobbles.
The length of the workpiece fed to the reheat furnace usually varies and a particular length is selected to satisfy a desired preselected shape and length of the final rolled product. Extensive inventory control and scheduling efforts are needed as well as the requirement to handle the variable lengths of the workpieces. This has a particularly adverse affect on the operation of the reheat furnace because the different lengths of the workpieces cover less than the maximum hearth area which reduce productivity as well as increase the cost of fuel.
To overcome these problems, the present invention provides a process for joining together workpieces in an end-to-end relationship after heating in a reheat furnace for continuous processing in a rolling mill or the like. Any preselected number of workpieces, such as billets, can be joined together for rolling a product having a desired shape and length after which the length of the continuously-rolled product is subdivided into required lengths. This minimizes losses due to cropping and reduces the probability of cobbles and other losses to the yield of the workpiece material. Moreover, the process enables charging workpieces having a uniform length into a reheat furnace to maximize fuel efficiency and minimize scheduling an inventory control.